A sash window arrangement disposed within a frame is well known. The frame is comprised of a pair of opposed vertical tracks or jams. The tracks are adapted to slidably guide a pair of sash windows within the frame.
Various types of balance systems are known and are used to counterbalance the weight of the sash window. In particular, block and tackle counter balance assemblies are known and have become popular due to their combination of relatively compact size and ease of installation. The block and tackle balance combines a system of pulleys and an extension spring mounted within a rigid balance channel for conversion of a high spring tension applied over a short working distance to a lower tension applied over a longer working distance. The extension spring is anchored at one end of the balance channel and the pulley system is anchored at the other end of the channel.
A traditional arrangement utilizing a block and tackle balance is disclosed in U.S. Pat. No. 5,530,991 to deNormand. In deNormand '991, an end of the balance channel is attached to the track via a hook or other intermediate structure. An end of a cord reeved through the pulley system and extending from a second end of the channel is attached, via a hook or other intermediate structure, to a shoe. This shoe is in turn attached to the window sash and slides therewith, within the track. An inverted block and tackle counterbalance system is disclosed by U.S. Pat. No. 6,041,476 to deNormand. In this arrangement, the end of the cord extending from the channel is attached to the track via a hook or other intermediate structure. The balance channel is then attached to the sash shoe via a hook or other intermediate structure such that the balance channel slides within the track as the window slides within the frame.
A disadvantage encountered with use of the block and tackle balance system is that it limits the range of slidable motion available to the window sash. This results in ultimately limiting the size of the opening available to an occupant of an enclosure during an event of emergency, such as a fire or other reason necessitating rapid egress. An additional disadvantage realized through use of the prior art block and tackle balance arrangements is that after extended use, the connecting mechanism between the balance channel and the sash shoe, or between the balance channel and the track, may deteriorate. This results in possible sudden detachment of the balance channel from the shoe or the track. If such detachment occurs, replacement of parts or other repairs resulting from the accompanying rapid movement of the block and balance channel and/or sash may be required.
The present invention is provided to solve these and other problems.